1. Field of the Invention
The present invention relates to a semiconductor device which is equipped with a semiconductor element, and to an optical pickup device which is equipped with the semiconductor device.
2. Description of the Related Art
Recently, in the field of optical disk devices which use semiconductor laser light, progress has been made in reducing thickness as devices are made more compact in size and lighter in weight. Therefore, semiconductor laser devices which are used as light sources in optical disk devices of this kind are also subject to urgent requirements for reduced thickness. In addition, there is the problem of the generation of heat due to an increase in the oscillating output of the semiconductor laser together with an increase in the writing and reading speed to and from an optical disk, and hence there is also a demand for good heat radiating properties. At the same time, there are also demands for increased strength in lead terminals in the manufacturing process for semiconductor laser devices.
Below, a conventional semiconductor laser device is described with reference to FIG. 6A, FIG. 6B, FIG. 7A and FIG. 7B.
FIG. 6A and FIG. 6B are diagrams showing the structure of the conventional semiconductor laser device in which the width of a lead terminal is increased; FIG. 6A is a plan diagram and FIG. 6B is a cross-sectional diagram taken along B-B in FIG. 6A.
In FIG. 6A and FIG. 6B, 1 is a die pad on which a semiconductor laser element is mounted; 29 is a lead terminal serving as an external terminal that is formed in an integral fashion with the die pad 1; 3 and 4 are lead terminals serving as external terminals that are formed without being connected to the die pad 1; 30 is resin of a frame structure which protects the semiconductor laser device, as well as insulating and fixing the respective lead terminals; and 6 is a base section which is formed in an integral fashion with the die pad. A lead frame is formed by the die pad 1, the lead terminal 29, the lead terminal 3, the lead terminal 4 and the base section 6. 7 is a cutting mark which is formed by cutting of a tie bar provided to ensure mechanical strength between the respective lead terminals when manufacturing the lead frame; the tie bar is cut at the very end of the manufacturing process of the lead frame. 17 is a semiconductor laser element, which is mounted on the die pad 1 via a sub mount 16. 18 is a wire which connects the respective lead terminals and the element 17. Here, the resin 30 is shown in a partially transparent fashion in order to clarify the shape of the lead terminals which are formed inside the same.
In the conventional semiconductor laser device shown in FIG. 6A and FIG. 6B, in order to ensure the strength of the lead terminals in the process for manufacturing a semiconductor laser device, an increased width section 10 is formed in which the lead width of the lead terminal 29 from the junction of the lead terminal 29 with the die pad 1 to the cutting mark 7 is formed to be thicker than the lead width of the other lead terminals.
FIG. 7A and FIG. 7B are cross-sectional diagrams showing the structure of a conventional thin semiconductor laser device; FIG. 7A is a plan diagram and FIG. 7B is a cross-sectional diagram taken along C-C in FIG. 7A. Furthermore, in FIG. 7A and FIG. 7B, the same reference numerals are assigned to compositional elements which are common to FIG. 6A and FIG. 6B, and further the description thereof is omitted here.
In the conventional semiconductor laser device shown in FIG. 7A and FIG. 7B, in order to achieve a thin width, the resin 30 provided on the rear surface with respect to the surface of the semiconductor laser device where the semiconductor laser element 17 is mounted is reduced in thickness. Even if the resin 30 provided on the rear surface is formed thinly, in order to ensure the holding strength of the lead terminal 29 and the adhesion of the resin 30, a bend section 8 is provided in the region of the lead terminal 29 which is covered with the resin 30 from the junction of the lead terminal 29 with the die pad 1, the die pad 1 including the base section 6 is formed into a shape which is cut down below the lead terminal 3, the lead terminal 4 and the bend section 8 of the lead terminal 29, and the resin 30 is provided below the region which includes the bend section 8, thereby making it possible to reduce the thickness of the resin 30 provided on the rear surface of the surface where the semiconductor laser element 17 is mounted. Moreover, it is also possible to completely remove the resin 30 which is provided on the rear surface portion of the surface where the semiconductor laser element 17 is mounted, and hence the rear surface of the semiconductor laser device can be made to coincide with the die pad 1. By this means, it is possible to form a semiconductor laser device into a thin dimension while maintaining a certain degree of holding strength for the lead terminals, and furthermore, by completely exposing the rear surface of the die pad 1, it is possible to improve the heat radiating effects by enlarging the contact surface area with a heat radiating plate.
However, there has been a problem in that if a composition is adopted which seeks to maintain the strength of the lead terminal and reduce the thickness of the semiconductor laser device by combining the characteristics of the two prior art semiconductor laser devices described above and increasing the lead width of the lead terminal 29 as well as providing the bend section 8 in the lead terminal 29, the amount of the resin 30 surrounding the lead terminal 29 is reduced in accordance with the increase in the lead width and hence the holding strength of the lead terminal 29 becomes insufficient. Conventionally, a composition has been considered for ensuring adhesiveness of the resin 30 by providing holes in the lead terminal which is covered with resin and causing the resin 30 to flow into these holes, but even in this case, generally the resin is formed so as to cover the whole surface of the semiconductor laser device, thereby ensuring the holding strength of the lead terminal, and in a composition where the resin 30 is not provided on the rear surface of the semiconductor laser device in this way, there have been problems in that the holding strength of the lead terminal cannot be ensured.